It has become relatively common for individuals to possess a number of different devices through which they communicate. For example, a person may have a home telephone, a wireless telephone, a pager, a personal digital assistant (PDA), and an office telephone to name a few. Today, it is common for a mobile device such as a cellular telephone or PDA to include both cellular (i.e., circuit switching) and data (i.e., packet switching) services, providing the user with the ability to wirelessly transmit and receive voice and data from the same device.
In addition, a mobile communication device may be designed to allow voice communications over two different wireless networks such as e.g., a wireless wide area network (WWAN) and a wireless local area network (WLAN). A WWAN is typically a cellular telecommunications network such as e.g., GSM (Global System for Mobile communications)/GPRS (General Packet Radio Service). A WLAN is typically an 802.11-based wireless network that allows voice over Internet Protocol (VoIP) communications. Typically, two different wireless transceiver portions of the mobile device are utilized for voice communications, one for the WWAN and another for the WLAN. Sometimes, it is desirable for the mobile device to switch between the WWAN and WLAN under certain circumstances. For example, the user may have a preference for VoIP calls on WLANs whenever a WLAN is available. In the field of wireless communications, however, the problem of seamlessly switching communications between the two incompatible wireless networks has not been adequately addressed.
One major issue is how to switch between the two different wireless networks without dropping an active call, such as a voice call, involving the mobile device. As an example situation, the mobile device may be compatible with both GSM/GPRS technologies and 802.11 technologies, but yet be unable to seamlessly switch between these networks during active calls. Moreover, it is desirable for this switching to take place without dropping the active call and, preferably, without letting either party on the call know that the switching has taken place.